Hot air baker's rack ovens are known in which the goods which are to be baked are introduced on baking sheets arranged on square or rectangular trays or pans held in a quadratic wheeled rack. The rack is intended to be introduced into the oven chamber of the oven and to remain there while the baking process takes place. The oven chamber has a rectangular, square or circular horizontal cross-section (i.e. the cross-section when viewed from above is rectangular, square, or circular) and is dimensioned to accept a rack and allow it to be rotated. Hot air can be introduced via one or two corner vents into the oven chamber to bake the goods. This leads to a temperature gradient across the oven chamber which can lead to uneven cooking of the goods. In order to reduce uneven baking of the goods, the rack is rotated around a vertical axis during the baking process. This can be achieved by placing the rack on a turntable during the baking process or by lifting the rack with a rotatable hook which is rotated during the baking process. Once the baking process is finished the rack is removed (after being lowered and decoupled from the hook if such a hook is used) from the open rack oven. An example of such a rack oven is known from U.S. Pat. No. 3,954,053. This has a substantially rectangular oven chamber with a straight back wall, two parallel, spaced-apart side walls arranged perpendicular to the back wall and a curved door able to close off the front end of the oven chamber.
In the following description features which are well-known in the art such as hot air supply and exhaust systems are not described in detail except where necessary to aid comprehension of the invention.
A conventional rack oven has an external housing which encloses an oven chamber, a hot air channel where hot air is about to flow and a hot air inlet in the form of a vertical series of horizontal openings in the wall of the oven chamber though which hot air is blown into the oven chamber, an exhaust outlet via which hot air is removed from the oven chamber and a door. As is normal in baker's ovens, at least some of the exhausted air is conveyed by a fan through suitable ducting past a heater and re-introduced into the oven chamber via hot air inlet.
The food products are placed on pans, trays, slings or other suitable supports in a wheeled rack which is transported into the oven chamber and the shape of the openings in the hot air inlet are preferably designed so that hot air will flow in a desired manner through the oven chamber. Preferably the hot air flow is arranged so that the heating of the goods being baked is even, with an even transfer of heat from the top to bottom of the rack and from the outer edge to the centre of the baking tray. This can be achieved by angling the opening upwards so that the air flows hit the baking trays at an upward angle to provide heat to the underside of the goods being baked. The products in the oven are thus heated by being directly touched by a stream of hot air as well as indirectly through the trays that they lie on. The wheeled rack is preferably supported from the ceiling of the oven chamber by a powered rack rotating mechanism for rotating the rack which rotates about a substantially vertical axis.
Hot air for cooking food in baker's ovens can be produced by burning a fuel in a burner and transferring the heat in the exhaust gases via a cross-flow tube heat exchanger to cooking air without the cooking air being contaminated by the exhaust gases.
One object when designing baker's ovens is to improve the energy efficiency of the oven and at the same time keep the footprint of the oven as small as possible without decreasing the baking capacity of the oven.
Steam is preferably used early in a baking procedure in order to influence the elasticity of the bread surface and in addition to make the surface glossy.
The steam is normally supplied via the hot air channel into the oven chamber via the openings.
The boiling speed affects the baking of the goods in an oven because the gluten on the surface crystalize and form a surface that can expand without cracks. Steam causes this by the wetting of the surface together with the immediate transfer of energy, when steam condensate to water on the surface on the dough. If steam is not added the surface dries and forms a dry surface. Therefore the speed of evaporation is important.
The object of the present invention is to achieve an improved steaming procedure of a baking or cooking procedure by increasing the evaporation speed and minimizing influence of the hot air flow during the main baking procedure.